Use -Werror in hardware/libhardware/modules

* Remove unused local variables.
* Remove or comment out unused static functions.
* Fix trivial bugs found by unused value warnings.

Bug: 66996870
Test: build with WITH_TIDY=1
Change-Id: I99389b883c89551850180d25241a35a40bb77b26
diff --git a/modules/vr/Android.mk b/modules/vr/Android.mk
index 0305745..2cdcb1b 100644
--- a/modules/vr/Android.mk
+++ b/modules/vr/Android.mk
@@ -23,6 +23,6 @@
 LOCAL_HEADER_LIBRARIES := libhardware_headers
 LOCAL_SHARED_LIBRARIES := libcutils
 LOCAL_MODULE_TAGS := optional
-LOCAL_CFLAGS += -Wno-unused-parameter
+LOCAL_CFLAGS += -Wall -Werror -Wno-unused-parameter
 
 include $(BUILD_SHARED_LIBRARY)